/*
*   Author:zuobufan
*   CreateTime:2022-01-21
* */
function bigimg(){
    var bbox = document.getElementById("box");
    var bmove = document.getElementById("move");
    var bbimg = document.getElementById("bimg");
    var b_bimg = document.getElementById("b_bimg");
    bbox.onmouseover = function(){//鼠标移动到box上显示大图片和选框
        bbimg.style.display = "block";
        bmove.style.display="block";
    }
    bbox.onmouseout = function(){//鼠标移开box不显示大图片和选框
        bbimg.style.display = "none";
        bmove.style.display="none";
    }
    bbox.onmousemove = function(e){//获取鼠标位置
        var x = e.clientX;//鼠标相对于视口的位置
        var y = e.clientY;
        var t = bbox.offsetTop;//box相对于视口的位置
        var l = bbox.offsetLeft;
        var _left = x - l - bmove.offsetWidth/2;//计算move的位置
        var _top = y - t -bmove.offsetHeight/2;
        if(_top<=0)//滑到box的最顶部
            _top = 0;
        else if(_top>=bbox.offsetHeight-bmove.offsetHeight)//滑到box的最底部
            _top = bbox.offsetHeight-bmove.offsetHeight ;
        if(_left<=0)//滑到box的最左边
            _left=0;
        else if(_left>=bbox.offsetWidth-bmove.offsetWidth)//滑到box的最右边
            _left=bbox.offsetWidth-bmove.offsetWidth ;
        bmove.style.top = _top +"px";//设置move的位置
        bmove.style.left = _left  + "px";
        var w = _left/(bbox.offsetWidth-bmove.offsetWidth);//计算移动的比例
        var h = _top/(bbox.offsetHeight-bmove.offsetHeight);
        var b_bimg_top = (b_bimg.offsetHeight-bbimg.offsetHeight)*h;//计算大图的位置
        var b_bimg_left = (b_bimg.offsetWidth-bbimg.offsetWidth)*w;
        b_bimg.style.top = -b_bimg_top + "px";//设置大图的位置信息
        b_bimg.style.left = -b_bimg_left + "px";
    }

}
